Circuit interrupter



Oct. 8, 1957 J. D. FINDLEY, JR

CIRCUIT INTERRUPTER Filed May 11, 1955v Fig.|.

Fig.2.

INVENTOR WITNESSES Joseph D. F|ndley,Jr. 6i 8Y1! United States Patent 9 CIR-SUIT INTERRUPTER Eoseph D. Findley, Jr., Forest Hills, Pa., assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application May 11, 1955, Serial No. 507,595

Claims. (Cl. 200-93) The invention relates to circuit interrupters and, more particularly, to high-speed circuit interrupters.

Circuit interrupters intended primarily for use as protective devices for reverse currents in the circuits of Mercury arc rectifiers must be made to open asqurckly as possible after the reverse current fault begins. In order to obtain fast mechanical action, such clrcuit 1nterruoters are usually equipped with electromagnetic holding devices which are polarized and arranged to release an armature when the current in the main conductor reverses.

Heretofore, the magnetic releasing action of the holding magnet has been achieved by passing the main conductor or bucking bar through the holding magnet in such a manner that, upon the occurrence of a reverse current, the magnetomotive force of the bucking bar opposes the magnetomotive force of the holding coil. This reduces the holding power of the holding magnet and permits release of the armature. This arrangement operated satisfactorily on previous installations involving relatively low power. However, some modern rectifier installations involve higher voltages and considerably higher power concentrations and consequently higher rates of rise of reverse current. With such higher rates of rise of currents, the magnetomotive force of the main conductors may completely overcome the holding coil and cause magnetic flux to build up in the reverse direction before the armature has had time to move away far enough to escape the magnetic pull. This results in retardation of the opening speed, and in extreme cases, may result in recapture of the armature by the holding magnet. Also, the close proximity of the large fault current conductor to the armature causes a magnetic attraction tending to reduce acceleration even after the armature has moved a short distance away from the magnet.

An object of the invention is to provide a circuit interrupter embodying a holding magnet in which the magnetic drag on the armature is substantially eliminated by causing the magnetic flux through the armature to decrease to approximately zero and to prevent increase of the magnetic flux in the reverse direction.

Another object of the invention is to provide a circuit interrupter embodying a high-speed holding magnet in which the main current conductor is disposed relative to the holding magnet in such a manner that the reverse current in the main conductor will reduce the flux holding the reverse current tripping armature to near Zero permitting quick release of the armature and also to prevent increase of the flux in the reverse direction in response to an increasing reverse fault current before the armature is mechanically accelerated away from the holding magnet.

Another object of the invention is to provide a circuit interrupter embodying a holding electromagnet that is highly sensitive to low values of reverse current.

Another object of the invention is to provide a circuit interrupter embodying holding electromagnetic means ICC that is highly sensitive for high-speed tripping in re p to low values of reverse current but which is relatively insensitive to forward overcurrents.

Another object of the invention is to provide a circuit interrupter embodying a holding magnet including two armatures having iiux paths for diverting the holding flux around the armatures according to the direction of flow of the current in the circuit controlled by the interrupter.

The invention, both as to structure and operation together with additional objects and advantages thereof, will be best understood from the following detailed description thereof when read in conjunction with the accompanying drawing.

in said drawing:

Figure 1 is a diagrammatic view showing a high-speed circuit interrupter embodying the principles of the invention.

Pig. 2 is a top plan view of the holding electromagnet and the flux diverting elements.

Pi g. 3 is a perspective view of the holding electromagnet.

Referring to Fig. 1 of the holding, the circuit interrupter comprises stationary contact means 11 and coopcrating movable contact means 13. The movable contact means is mounted on a pivoted switch arm 15 biased in opening direction by a spring 17. The switch arm 15 is normally held in the closed position by means of a holding magnet indicated generally at 19, which includes a pair of armatures 21 and 23. The armatures 21 and 253 are connected to opposite ends of a bar 25 by links 27, and a link 29 is pivotally connected at its lower end to the mid-portion of the bar 25. The upper end of the iink 29 is pivotally connected by means of a pivot pin 31 to one end of a link 33 which has its other end pivotally connected to the switch arm 15. One end of a link 35 is pivotally connected to the links 29 and 33 by the pivot pin 31, and the other end of link 35 is connected by means of a pivot pin 37 to a link 39 which has its other endpivoted on a fixed pivot. One end of a toggle link 41 is pivotally connected to the links 35 and 39 by the pivot pin 37. The other end of the toggle link 41 is connected by a knee pivot pin 43 to a toggle link 45, which is mounted on a fixed pivot 47.

in the closed position of the circuit interrupter with the armatures 21 and 23 in their attracted positions, a component of the force of the spring 17 holds the toggle 41-45 in an overset position against a fixed stop 48 and above a line through the centers of the pivots 37 and 47, thus maintaining the switch arm 15 in the closed contact position against the force of a spring 49 which tends to cause collapse of the toggle 4145.

When either the forward armature 21 or the reverse armature 23 is released by the holding magnet the links 29 and 33 are free to move in opening directions with the link 35 pivoting about the pivot pin 37 to effect highspeed opening of the breaker contacts under the influence of the spring 17. Release of either of the armatures 21-433 also removes the force applied to the toggle 4145 and the spring 49 causes collapse of this toggle.

Collapse of the toggle 4145 causes a pin 51 on the end of the toggle link 45 opposite the knee pivot pin c to move upwardly in an elongated slot 53 in a link 55. The lower end of the link 55 is connected by means of a pivot pin 57 to a crank arm 59. Collapse of the toggle 4145 also effects movement of the released armature 21 or 23 to its attracted position, where it is held upon correction of the abnormal circuit condition which effected release of one of the armatures. With both of the armatures 2123 held in their attracted positions, rotation of the crank arm 59 draws the link 55 downward during which movement the upper end of the slot 53 engages the pin 51 and resets the toggle 4145 to its overset position and, at the same time, acting through the links and 33 moves the switch arm 15 to the closed contact position.

The holding electromagnet 19 comprises a U-shaped core 61 of solid iron and laminated pole pieces 63, 65, and 67. The pole pieces 63 and 65 between them form an air gap 69, and the pole pieces 65 and s7 form an air gap 71, the air gap 69 being adjacent the forward armature 21 (Fig. 1) and the air gap 71 being adjacent the reverse armature 23. A pair of coils 73 are accumulatively wound on the legs of the U-shaped core 61 to produce a magnetic flux that traverses the air gaps 69 and 71 adjacent the armatures 21 and 23. The coils 73 are connected to a suitable source of electrical energy 75.

As shown in Fig. 2, the current path adjacent the holding magnet comprises substantially parallel main conductors 77 and 79 which are joined at the ends by a conductor 81 connected to a source and a conductor 83 which is connected to the moving contact of the interrupter to form solid conducting paths. The current path through the breaker extends from a conductor 86, stationary and movable contacts 1113, a conductor 84, the conductor 33 parallel main conductors 77 and 79 and the conductor 81 to a conductor 32. Associated with the main conductor 77 is a forward flux shunt or diverter 85 comprising a U-shaped member of laminated magnetic material having one leg 87 thereof disposed adjacent the pole piece 63 with an air gap therebetween. The other leg 89 of the flux diverter 85 is disposed adjacent one leg of an inverted U-shaped member 91 which is also of laminated magnetic material and extends transversely across the center pole piece 65 between the armatures 21 and 23. Similarly disposed adjacent the opposite side and end of the holding magnet is a U-shaped reverse flux shunt or diverter 93 of laminated magnetic material having one leg 95 disposed adjacent the pole piece 67, and the end of the other leg 97 disposed adjacent the other leg of the inverted U-shaped center member 91. Suitable air gaps are provided respectively between the legs 95 and 97 and the pole piece 67 and the member 91. An air gap is also provided between the U- shaped center member 91 and the center pole piece 65.

The conductors 77 and 79 may comprise one or more conducting members, two being shown for illustrative purposes. It will be seen from Fig. 3 that only one conductor forms a series energizing coil or winding, indicated at 77a, by passing through the loop of the forward flux diverter 85; whereas, all of the conductors 79 pass through the loop of the reverse flux diverter 93, thus forming a series energizing coil or Winding for this diverter. By this arrangement, the electromagnet is made relatively insensitive to a low rise in forward current but highly sensitive to a low value of reverse current.

With the holding coils 73 (Fig. 1) energized and normal forward current flowing in the parallel conductors 77 and 79, the flux path is as shown by the arrows in Fig. 1; that is, through the core 61, pole piece 67, armature 23, center pole piece 65, armature 21 and pole piece 63, thus maintaining both of the armatures 21 and 23 in their attracted positions and holding the movable switch arm 15 in the closed contact position. Upon a predetermined rise of current in a forward direction, the current in the energizing coil 77a causes the flux to be shunted through the laminated member 85 around the air gap 69, thus reducing the magnetic flux through the armature 21 to approximately zero causing high-speed release of the armature 21 and opening of the interrupter contacts in the manner previously described.

When the direction of current flow is reversed, the energizing coil of the main conductor 79 causes the magnetic flux to be shunted through the diverter path 93 around the air gap 71 reducing 'the magnetic flux through 6 the armature 23 to approximately zero causing high-speed release of the armature 23.

A member 99 (Fig. 1) of high conductive material such as copper, is mounted on and surrounds both legs of the U-shaped core 61 of the holding magnet to retard the change in flux in this portion of the magnet during the short interval while the armature is moving away from the pole pieces. The member 99 comprises a single solid copper member having spaced openings therein to fit over the legs of the core 61. The flux in the core member 61 induces currents in the copper member 99 which produce a flux field of their own opposing the flux in the magnet core 61 thus limiting or retarding the change in flux in the core 61 at the time the current in the main conductors reverses.

A laminated iron choke 101 (Fig. 2) is placed around the main conductor 77 in inductive relation thereto in order to increase the impedance of the main conductor 77 in response to reverse fault currents. This limits the amount of reverse fault current flow through the con ductor 77 and increases the reverse fault current through the main conductor 79 thereby increasing its sensitivity of the magnet to low values of reverse fault currents and makes the magnet relatively insensitive to low rises in forward fault currents.

By varying the number of turns of the main conductors 77 or 79, or both, numerous variations and combinations of forward and reverse tripping characteristics may be obtained. Also, by properly relating the proportions of the iron in the holding magnet, the sizes of the air gaps and the number of turns of the main conductors any desired tripping sensitivity for a. given rate of current rise may be obtained.

It will be noted that the main conductor does not extend through the U-shaped iron core 61 but only through the separate outside laminated flux diverter loop. The holding coil magnetic circuit 61 is made of solid iron or steel so that eddy currents will retard change of flux through this path, while the armatures 21 and 23, pole faces 63, 65 and 67 and the flux diverting paths and 93 are laminated to permit quick change of flux. The cross sections of the flux diverting paths are so chosen relative to the amount of magnetic flux existing in the armature prior to the occurrence of a fault current that the outside flux diverting path will be magnetically saturated when this amount of flux has transferred to the outside diverting path. For this reason the flux through the armature reduces to near zero until the slowly changing flux through holding core iron path 61 increases, thus permitting movement of the armature away from the pole facis before the flux builds up in the holding coil magnetic pat It will be seen that the invention provides a high-speed circuit interrupter having a holding electromagnet that is highly sensitive to low values of reverse current and relatively insensitive to a rise in forward current.

While the inventionhas been disclosed in accordance with the provisions of the patent statutes, it is to be understood that various changes in the structural details and arrangements of parts thereof may be made without departing from the spirit of the invention.

1 claim as my invention:

1. A circuit interrupter having relatively movable contacts, an electromagnet for holding said interrupter closed comprising a pair of armatures operatively related to one of said contacts, a U-shaped magnet yoke having a plurality of pole pieces spaced to provide an air gap adjacent each of said armatures, holding coils cooperating to hold said armatures in attracted position to thereby hold said interrupter closed, release of either of said armatures effecting opening of said interrupter, a first magnetic path by-passing one of said armature air gaps, a second magnetic path by-passing the other of said armature air gaps, parallel main current conductors on opposite sides of said pole pieces for energizing said magnetic paths, one

of said main current conductors energizing said first magnetic path in response to a rise in forward current flow to effect release of one of said armatures, and the other of said main current conductors energizing said second magnetic path in response to reverse current flow to effect release of said other armature.

2. A circuit interrupter having relatively movable contacts, an electromagnet for holding said interrupter closed comprising a pair of spaced armatures operatively related to each other and to one of said contacts, a magnet yoke, a plurality of pole pieces spaced to provide air gaps adjacent each of said spaced armatures, a magnetic path including said armature air gaps and said pole pieces, a first iron magnetic path by-passing one of said armature air gaps, a second iron magnetic path bypassing the other of said armature air gaps, an energizing winding for each of said iron magnetic paths connected in series in the circuit to be controlled by the interrupter, one of said windings being responsive to predetermined rise in forward current to effect release of one of said armatures and opening of said contacts, and the other of said windings being responsive to reverse current to effect release of said other armature and opening of said contacts.

3. A circuit interrupter having relatively movable contacts, a holding electromagnet for holding said interrupter closed comprising a pair of armatures operatively related to one of said contacts, a U-shaped magnet yoke having holding coil means thereon, a pair of pole pieces one disposed at each leg of said magnet yoke, a third pole piece disposed between said pair of pole pieces and spaced thereupon to provide magnetic air gaps adjacent each of said armatures, a first iron magnetic path disposed at one side of said pole pieces by-passing one of said armature air gaps, a second iron magnetic path disposed on the opposite side of said electromagnet and by-passing the other of said armature air gaps, parallel conductors on opposite sides of said electromagnet, each of said conductors including a winding for energizing said iron magnetic paths, one of said windings being responsive to abnormal forward flow of current to effect release of one of said armatures and opening of said contacts, and the other of said windings being responsive to reverse flow of current to effect release of the other of said armatures and opening of said contacts.

4. A circuit interrupter having relatively movable contacts, an electromagnet forholding said interrupter closed comprising a pair of armatures operatively related to one of said contacts, release of either one of said armatures effecting opening of said contacts, a magnet yoke having holding coil means thereon, a pair of pole pieces one disposed at each end of said magnet yoke, a center pole piece disposed between said pair of pole pieces and spaced therefrom to provide magnetic air gaps adjacent each of said armatures, a magnetic path including said pole pieces and said armatures, a first flux diversion path at one side of said electromagnet including said center pole piece and one of said pair of pole pieces by-passing one of said armature air gaps, a second flux diversion path at the opposite side of said electromagnet including said center pole piece and the other of said pair of pole pieces bypassing the other of said armature air gaps, a winding for each of said flux diversion paths, one of said windings being energized in response to abnormal current flow in one direction to induce a flow of flux around one of said armature air gaps and thereby effect release of one of said armatures, the other of said windings being energized in response to reverse current flow to induce a flow of flux around the other of said armature air gaps and thereby eifect release of said other armature.

5. In a circuit interrupter having relatively movable contacts, an electromagnet for holding said interrupter closed comprising a pair of armatures either of which armatures when released effects opening of said contacts, a magnet yoke having holding coil means thereon, an end pole piece at each end of said magnet yoke, a center pole piece between said end pole pieces and spaced therefrom to provide magnetic air gaps for each of said armatures, magnetic flux diversion paths comprising a member of magnetic material disposed transversely across said center pole piece, a first U-shaped member of magnetic material on one side of said pole pieces having one leg disposed adjacent one end of said transverse member and the other leg adjacent one of said end pole pieces, a second U-shaped member of magnetic material on the other side of said pole pieces having on leg disposed adjacent the other end of said transverse member and the other leg adjacent the other of said end pole pieces, a Winding for each of said U-shaped members, one of said windings being responsive to current flow in one direction to cause the magnetic flux to by-pass one of said armature air gaps and effect release of said one armature, and the other of said windings being responsive to reverse current flow to cause the magnetic flux to bypass the other of said armature air gaps and effect release of said other armature.

6. A circuit interrupter having relatively movable contacts, an electromagnet for holding said interrupter closed comprising an armature operatively related to one of said contacts, a magnet yoke of solid magnetic material having holding coil means thereon, laminated pole pieces spaced apart to provide a magnetic air gap adjacent said armature, a magnetic flux path including said pole pieces and said armature air gap, a fixed laminated flux shunt path extending at one side of said electromagnet and bypassing said armature air gap, and a main current conductor disposed at one side of said electromagnet and having a series winding energizing said fixed laminated shunt path in response to abnormal current conditions to cause the magnetic flux to by-pass said armature air gap and effect release of said armature.

'7. A circuit interrupter having relatively movable contacts, an electromagnet for holding said interrupter closed comprising an armature operatively related to one of said contacts, a magnet yoke of solid magnetic material having holding coil means thereon, laminated pole pieces spaced apart to provide a magnetic air gap adjacent said armature, a magnetic flux path including said pole pieces and said armature air gap, a fixed laminated flux shunt path by-passing said armature air gap, and a main current conductor disposed outside said magnet yoke and having a series winding energizing said fixed laminated shunt path in response to abnormal current conditions to cause the magnetic flux to by-pass said armature air gap and eifect release of said armature.

8. A circuit interrupter having relatively movable contacts, an electromagnet holding said interrupter closed comprising a pair of armatures operatively related to one of said contacts, a U-shaped magnet yoke having holding coil means thereon, a plurality of pole pieces spaced to provide an air gap adjacent each of said pair of armatures, release of either of said armatures effecting opening of said interrupter, a first magnetic path by-passing one of said armature air gaps, a second magnetic path by-passing the others of said armature air gaps, parallel main current conductors on opposite sides of said magnet yoke for energizing said magnetic paths, one of said main current conductors energizing said first magnetic path in response to a rise in forward current flow to effect release of one of said armatures, the other of said main current conductors energizing said second magnetic path in response to reverse current fiow to effect release of said other armature, and means of magnetic material disposed in inductive relation with said one main current conductor and responsive to reverse current flow to increase the impedance of said one main current conductor to thereby increase the reverse current flow in said other main current conductor.

9. A circuit interrupter having relatively movable contacts, an electromagnet holding said interrupter closed comprising a pair of armatures operatively related to one of said contacts, a U-shaped magnet yoke having holding coil means thereon, a plurality of pole pieces spaced to provide an air gap adjacent each of said pair of armatures, releasing either of said armatures effecting opening of said interrupter, a first magnetic flux path by-passing one of said armature air gaps, a second magnetic flux path by-passing the other of said armature air gaps, parallel main current conductors one disposed on each side of said magnet yoke for energizing said magnetic flux paths, one of said main current conductors energizing said first magnetic flux path in response to a rise in forward current flow to cause the magnetic flux to be diverted around one of said armature air gaps and effect release of one of said armatures, the others of said main current conductors energizing said second magnetic flux path in response to reverse current flow to cause the magnetic flux to be diverted around the other of said magnetic air gaps and efiect release of said other armature, and means comprising a member of high conductivity disposed in inductive relation with said magnet yoke producing a magnetic flux retarding reverse flux build-up in said magnet yoke in response to reversal of current flow in said main conductors.

10. A circuit interrupter having relatively movable contacts, an electromagnet holding said interrupter closed comprising a pair of armatures operatively related to one of said contacts, a U-shaped magnet yoke having holding coil means thereon, a plurality of pole pieces spaced to provide an air gap adjacent each of said pair of armatures, release of either of said armatures effecting opening of said interrupter, a first magnetic flux path by-passing one of said armature air gaps, a second magnetic flux path lay-passing the other of said armature air gaps, parallel main current conductors one disposed on each side of said magnet yoke for energizing said magnetic flux paths, one of said main current conductors in response to a rise in forward current energizing said first magnetic flux path to cause the magnetic flux to be diverted around one of said armature air gaps and effect release of one of said armatures, the other of said main current conductors in response to reverse current flow energizing said second magnetic flux path to cause the magnetic flux to be diverted around the other of said magnetic air gaps and effect release of said other armature, means of magnetic material disposed in inductive relation with said one main current conductor and responsive to reverse current flow to increase the impedance of said one main current conductor to thereby increase the reverse current flow in said other main current conductor, and means comprising a member of high conductivity disposed in inductive relation with said magnet yoke responsive to reversal of current flow in said main conductors to retard reverse flux build-up in said magnet yoke.

References Cited in the file of this patent UNITED STATES PATENTS 1,995,894 McNairy Mar. 26, 1935 FOREIGN PATENTS 456,762 Germany June 21, 1929 648,879 France Aug. 20, 1928 719,917 Great Britain Dec. 8, 1954 

